Small Engines (Lawn Mowers, etc.): 6HP Briggs & Stratton, briggs stratton, float bowl

Question
Eric,

You are correct my primer does indeed have a small hole in the center of the bulb.



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Followup To
Question -
My primer does not fill with fuel. It filled with fuel when I continually pushed it to keep the engine running. That is why the gasket got soaked.

I believe the bulb is solid.

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Question -
I thought the primer bulb was supposed to blow air into the float bowl, which is why I decided to replace the gaskets after pushing the primer so many times that it actually filled with liquid gasoline and saturated the gasket, & the spray carb cleaner toasted the o-ring for the floatbowl.

My float bowl is attached by a banjo type bolt not a nut. I can see through all the holes in the bolt.

Yes the holes on the air-filter side of the carb are clear, I can spray carb cleaner through them and it comes out under pressure also.

The mower does have an adjustable throttle (as well as a governor I believe).

I don't know what a blower housing is. I have played with what I believe to be a governor linkage that goes under the starter housing w/o removing the housing. I have also manually operated the butterfly in the carb w/o using the cable attached w/o any luck at keeping it running.

I guess I'll remove the starter cover and check the linkage at that end.

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Question -
yes the primer is in the air filter housing.

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Question -
No I have not removed the primer bulb. When I was pushing the primer over and over to see if the engine would continue to run the bulb filled with gas. When I removed the airfilter housing the fuel drained from the bulb. Upon reassembling the carb and housing the primer worked again.

How do I remove the bulb and do I check it or just replace it?

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Question -
Eric,

The carb has a separate floatbowl attached with a 1/2" head possibly 3/8" shank banjo bolt. The float is white, the needle valve slides in a track on the float.

I hope this helps in someway. I have lots of numbers from all over the carb if that would be more helpful.

What's a 2 piece carb?


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Question -
Eric,

When I was first trying to determine if anything was clogged I used a 27 1/2 ga hypodermic needle (incredibly small) through the ports. I don't remember exactly but I believe that there was only one small port, possibly only the one for the primer but there might have been one more. I'll reattempt the probing tomorrow in the light and let you know if I have any success. What's the price of a used carb? If you can't sell them then suggest a fair price so I don't get screwed elsewhere please.

Thanks
Pat
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Question -
Eric,

I purchased the mower probably something like 8 years ago. However it was almost never used. That is why I know how low the hours are on the carb.

It was purchased at WalMart where they don't know or possibly even comprehend anything.

Pat

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Question -
Eric,

The O-ring seal from the carb to the head/intake manifold is new. The intake manifold is really just a straight piece of tube only one inch or so pressed into the head. If this was somehow defective wouldn't the engine fail to run regardless of how the fuel mixture reached this point?


No I did not use compressed air to blow out the carb. I used an aerosol can of carb cleaner. I did take the carb to the local B&S dealer where I purchased the gasket/seal set. Before installing/assembling the carb I showed it to the tech there he looked at the ports shined his flashlight through it etc. And then shrugged his shoulder. He said it looked good and didn't know what the problem could be. This is an incredibly simple carb. There aren't any adjustment screws, choke or anything that could go wrong in my opinion except for varnish or physical damage.

I am absolutely certain that this carb has less than a total of 10 hours on it & the engine. I just don't understand what could be wrong. The B&S guy wanted me to buy another carb. I don't want to shell out the money unless I absolutely know that a new carb will fix the problem. Plus I would really like to know what is wrong with this carb whether or not I purchase a new carb.
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I have a 6hp I believe 191cc B&S Diamond engine on a walk behind mower. Not OHV. I believe this is a 1996 engine. I purchased it new. I believe it has less than 10 hours total on the engine. The engine will not continue to run after being primed.

I can prime w/gas directly into the throttle body or using the bulb primer. The engine starts flawlessly however it does not continue to run. If I continuously use the primer button or supply gas directly into the throttle body it will run at any throttle setting.

This model carburetor doesn't have a choke. There isn't any adjustment screws, I have taken the carb apart and replaced all gaskets & O-rings. Condition remains. I asked at my B&S dealer who didn't have any suggestions.

I sprayed all openings/ports w/CRC carb cleaner. I can see light through them. The main jet is clear. I believe all ports are open. It had very little varnish inside the carb. There doesn't appear to be any cracks and I know that the carb has never been bumped, banged or traumatized. I don't think there are any vacuum leaks.

The carb is not flooding and the float bowl seems to be full all the time. There isn't a fuel filter on the carb or inline. Fuel flows freely from the fuel line. I emptied the tank completely and replaced with fresh gas.

I have tried running w/o an air filter to ensure that wasn't the problem. Same with muffler.

I am open to any suggestions. I just can't figure out why there isn't enough venturi effect to cause the fuel to be drawn into the throttle body.
Answer -
Since the engine will run while being primed or with aux fuel then you know the compression, ignition and timing are fine.

The problem must lie in the carb or intake system.  Did you check the intake tube/pipe and gasket?

If so and these are fine then the problem must still be the carb.  

Did you use an air compressor to blow/clean the carb orfices?

Let me know.
Eric
Answer -
If the engine has less than 10 hours then the warranty should cover a defective carb.  Most warrenty problems develop within 10-20 hours of operation.

We see the symptoms you described very often...probably the most common problem.  A good carb cleaning almost always fixes the problem.

Where did you purchase the machine?
Do they have a warranty department?
Let me know.
Eric
Answer -
Based on the mowers age I'd guess you have an L head engine.

From what you have described the problem must be in the carburetor.  

You can run a piece of repair tag wire or similar small wire through the carb orfices to see if any of the holes are plugged.  

I know lots of mechanics who use the light test on carbs but I prefer not to use it...I've had several Tecumseh carbs that passed some light but the carb orfice was partially blocked.  A good cleaning with compressed air from an air compressor almost always fixes the problem.  If the carb still isn't working then we boil it in a strong acidic solution for 24 hours, rinse clean and use compressed air again.

If the carb still does not work then we use the tag wire method.  You can actually see the wire in the orfices and it normally will clean out what ever debris was blocking the orfice.

If you have performed all 3 techniques and still have no results then I would find a used carb and try it.  We have tons of used carbs at our shop specifically for cases like yours.

Does this help?

Eric
Answer -
Is your carb a float style carb or a two piece tank/carb combination?

Let me know.
Eric
Answer -
You have the better carb.  Have you removed the primer bulb and cleaned behind it?

I recall one or two carb where we had to remove the primer and replace the red rubber seal/check ball assembly.

I have never had one of these style carbs that could not be cleaned and repaired.  We have never had to "boil" these carbs either; just clean them with compressed air and they have always worked.

Let me know if you decide to remove the primer bulb.

Eric
Answer -
Got to thinking some more, scary, but is your primer bulb in the air filter housing.  If so there is no check valve in that system.

Let me know.
Eric
Answer -
When you press the primer bulb it sends a small air pulse into the carburetor bowl forcing fuel up the main throttle tube which allows the engine to start.

This style of carb is very reliable and we haven't ever had to replace one.

Can you see holes in the float bowl nut?  These holes are the high speed holes which deliver fuel to the engine via the main fuel tube. There are also a few holes on the air filter side of the carb that allow air to enter the carb bowl.  Are these holes clean?

Is you mower a fixed speed type or do you have a throttle cable?

Have you removed the blower housing and checked the governor linkage.  We frequently find grease/dirt near the governor linkage that will affect engine performance.

Let me know what you find.
Eric
Answer -
From everything you have described the primer bulb should not fill with fuel.  The primer bulb setup in the air filter housing forces air into the carb bowl which forces fuel up the emulsion tube.

Is the primer still filling with fuel?  The primer bulb for you engine should have a small hole in the center.  The other style primer bulb is solid.

Which one do you have?
The blower housing is the same thing as the starter housing.

Let me know about the primer bulb.
Eric
Answer -
Your bulb should have a vent hole in it.  The solid primer bulb is for the diaphragm vacu-jet carb set-up.  

Do you by chance have the old, orginal primer bulb?

Let me know.
Eric

Answer
If the mower is still not running then the carb may be defective.  You've cleaned the carb, checked the intake tube gaskets/o-ring, cleaned behind the primer bulb, checked the air filter housing to carb gasket then about the only thing left is to replace the carb.  

I would try some of you local repair shop to see if they have any used carbs or find a friend with a similar mower and borrow their carb to find out for sure.

The other option is to remove all the plastic carb parts and try soaking the carb in a carb solution and cleaning again.

Let me know what you decide to do.
Eric